WASHINGTON (MarketWatch) -- Signaling continued housing-market momentum, the S&P/Case-Shiller 20-city composite index rose 0.3% in February and was up 9.3% from the same period in the prior year, which is the largest year-over-year growth since May 2006, according to data released Tuesday. February's monthly growth was the largest since August. On a seasonally adjusted basis, prices rose 1.2% in February. All 20 cities saw year-over-year gains in February, with faster growth in 16 cities. Phoenix posted the largest year-over-year price growth at 23%, while New York had the lowest at 1.9%. With ongoing low interest rates, increasing demand and constrained inventory have been supporting prices. However, despite recent gains, the 20-city composite index indicates that prices remain about 29% below a 2006 peak.